If $x= r \sin \theta \cos \phi , y = \sin \theta \sin \phi $, and $z= r \cos \theta ,$ then

Question

$\begin{array}{1 1}(A) \; x^2+y^2+z^2=r^2 \\(B)\; x^2+y^2-z^2 =r^2 \\(C)\;x^2-y^2+z^2=r^2 \\(D)\;z^2+y^2-x^2=r^2 \end{array}$